precise stack scanning for Nim's GCs; work in progress

compiler/options.nim

@@ -140,12 +140,13 @@ var
   gEvalExpr* = ""             # expression for idetools --eval
   gLastCmdTime*: float        # when caas is enabled, we measure each command
   gListFullPaths*: bool
-  isServing*: bool = false
+  gPreciseStack*: bool = false
   gNoNimblePath* = false
   gExperimentalMode*: bool
 
 proc importantComments*(): bool {.inline.} = gCmd in {cmdDoc, cmdIdeTools}
 proc usesNativeGC*(): bool {.inline.} = gSelectedGC >= gcRefc
+template preciseStack*(): bool = gPreciseStack
 
 template compilationCachePresent*: untyped =
   {optCaasEnabled, optSymbolFiles} * gGlobalOptions != {}